[development] new install hook examples, .install files

[Chad Phillips -- Apartment Lines]

i spent a few hours getting my HEAD modules using the new core  
install hook.  i found the developer docs to be just a bit confusing,  
but was able to get things right after a bit.

anybody who's interested in looking at some working examples, see  
eventrepeat.install or signup.install in HEAD contrib.  since the  
hook is called from a full bootstrap, you can actually do a heck of a  
lot more than just install tables--in my case i also displayed some  
user messages regarding the status of the module installation, and in  
eventrepeat's case, i invoked eventrepeat_cron() to autopopulate a  
table w/ current date information.  i'm loving this change!  :)

chad